The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. The OSI model partitions a communication system into abstraction layers. The original version of the model defined seven layers.
The OSI model is hierarchical, in that a layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by the layer(s) above it, and uses the next lower layer to send and receive packets that are transported through that path.
Layer-4 of the OSI model is also referred to as the Transport Layer, and provides host-to-host communication services for applications. It provides services such as connection-oriented data stream support, reliability, low control, and multiplexing. A well-known transport layer protocol is Transmission Control Protocol (TCP). TCP is used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions. TCP is the more complex protocol, due to its stateful design incorporating reliable transmission and data stream services. Other prominent protocols in this group include Datagram Congestion Control Protocol (DCCP) and Stream Control Transmission Protocol (SCTP).
Other conceptual models for characterizing and standardizing the communication functions of a telecommunication or computing system are known. Some of these conceptual models utilize a layered hierarchy, while others do not. However, in all cases, the network model provides functionality corresponding to that of the OSI layer-4 Transport layer. Accordingly, it will be appreciated that references in the present disclosure to the OSI layer-4, or layer-4 functions, are not strictly limited to the OSI model, but instead also apply to equivalent conceptual abstractions and functionality in other networking models. Similarly, references in the present disclosure to TCP connections and messages shall be understood to refer to transport layer connections and messages defined under any suitable layer 4 protocol.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.